JPS602905A - Manufacture of diffusion type glass waveguide - Google Patents

Abstract

PURPOSE:To form a low-loss optical waveguide which has excellent consistency with a quartz glass optical fiber by devising the structure of a metallic film as a diffusion source. CONSTITUTION:This is one example of implementation. An alpha-Si film 21 which is 3mum thick is formed on a quartz glass substrate 1 which is 2mm. thick, and an alpha- Ge film 22 which is 0.3mum thick is further formed. Then, AZ1350J is used as photoresist and CBrF3 is used as etching gas to pattern the composite film of the films 21 and 22 linearly to a 6mum width. Glass particulates are blown thereupon and deposited to form a porous glass film 23 which is 1mm. thick. This is sent into an electric furnace and heated up to 1,100 deg.C at a 200 deg.C/hr speed in an atmosphere of oxygen and vapor in 1:1 proportion, and the body is held at 1,100 deg.C for 24hr to oxidize Si simultaneously with the diffusion of Ge. Thus, the optical waveguide 22b and a transparent glass film 24 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a glass optical waveguide used in the field of optical communications.

With the advancement of optical communication systems, the use of optical fibers in planar glass waveguides, which constitute optical components with functions such as optical branching and optical coupling, is increasing.
The importance of j is increasing.

Conventionally, as a manufacturing method for this type of glass waveguide, T, #, etc. are placed on desired portions of a multi-component glass glass plate.

A method has been proposed in which ions such as K, Ag, etc. are selectively diffused to increase the refractive index value of that part, thereby forming a leading waveguide. Although this method allows the formation of a leading waveguide relatively easily, there are concerns about long-term reliability because it uses multi-component glass as a material, and it is also directly fused with silica glass-based optical fibers, which are the mainstream of optical fibers. There was a problem in that it was impossible to make an XIF connection, and failures were likely to occur at the connection part with the optical fiber.

One conceivable way to solve the above problem is to use silica-based glass as the waveguide material, but it is impossible to use ion diffusion means with silica-based glass. As an alternative to ion diffusion, the conventional method @1 (a)
The method shown in (d) has been proposed (Japanese Patent Application No. 1983).
(No. 97017 “N method for optical waveguide”). That is, (
a) Quartz glass substrate] For example, G, metal film 2 is placed on top of 0.1
The film is formed to a thickness of about .mu.m by a vapor deposition method, and then (b) a photoetching method is used to leave the G and film z& in a desired pattern. Next, (c) porous glass II/J3 made of glass fine particles synthesized by thermal elongation or hydrolysis reaction of a glass-forming raw material gas containing SIC,,e, as a main component is covered in a pattern G and the film 2a. It is deposited on the substrate l as shown in FIG.

Finally, the substrate 1 is heated to about 1300° C. to diffuse the patterned Ge film into the porous glass film as a diffusion source for controlling the refractive index, and oxidizes the Ge metal to dissolve it in the glass fine particles. Finally, a transparent glass film 4 including an optical waveguide 2b was obtained (FIG. 1(d)). Although this method is a clever one that focuses on the high diffusion rate within the porous glass membrane, it has the following problems.

That is, in FIG. 1 (A-A crossing the optical waveguide in 6)
The refractive index 41 distribution on the ' plane exhibited a markedly asymmetric shape with the highest value at the boundary with the substrate 1, as shown in FIG. 1(e). Therefore, there is a drawback that the matching with the refractive index distribution of the optical fiber is poor, leading to a decrease in the coupling efficiency with the optical fiber.

The present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional methods, and is to improve the structure of the gold film as a diffusion source.

The drawings will be described in detail below.

FIGS. 2(a) to 2(d) are diagrams showing an embodiment of the present invention. (a) First, a Si film 21 is formed on a substrate l.

Next, (h) forming a Ge thin film 22 on the side 21 of s to form a composite film; (C)
The tetraconjugate membrane is patterned by manual beating with a roughy to obtain a patterned composite membrane 22a. Next, as in the conventional method, (d
) Porous glass rf423 is deposited and finally heated to G
e is diffused into the porous glass membrane 23 and the underlying 5siII and oxidized, finally forming a
A transparent glass film 24 including an optical waveguide 22b as shown in FIG.
get.

The refractive index distribution of the 84' plane of (el) in FIG. 2 gradually rises from the boundary with the substrate l as shown in (fl).

The symmetry is greatly improved compared to (e). This is due to the effect of the Si film formed prior to the Ge film.

Next, specific examples of the present invention will be described.

In Fig. 2, the substrate 1 has a thickness of 2 mm and a surface of Ml 5.
A crnX 5 rm quartz glass plate was used. An amorphous SL (a-8i) film 21 with a thickness of 3 μm was formed on one side of the optically polished surface by sputtering, and then
Amorphous Ge (
A-Ge) film 22 was formed. Next, AZ1350J is 7
A composite film of a-Si and a-Ge was patterned into a linear pattern of 6 μm (tli) using a sputter etching method using CBrF3 as an etching gas as an optical resist.

SsC on porous glass, glass fine particle synthesis,
Glass fine particles synthesized by a flame hydrolysis reaction using an oxyhydrogen flame were deposited by spraying on a substrate l having a patterned composite film. The thickness of the porous glass plate 23 is 1 mm.

During a busy period, a substrate covered with a porous glass film was placed in an electric furnace, and the rate of 2 Qo'c/hour was set in an atmosphere of 1:1 (volume ratio) + 7) W of oxygen and water vapor. The temperature was raised at 1100°C and held for 24 hours to diffuse G and oxidize G and sl.
The temperature was raised to 0°C in 100'07 hours, and the porous glass was completely transformed into transparent glass. Steam as the furnace atmosphere has the effect of promoting the oxidation of a-81.

Figure 3 (same color) shows the finally obtained refractive index distribution of the leading waveguide as a contour map. Figure 3 (a) shows the pattern shapes of GCa-8L and a-Go for reference. The cross-sectional structure of the composite membrane is shown. , (a) As can be seen from the comparison with (a), the center 31 of the refractive index distribution has moved above the position of the a-G film as a diffusion source. This is because the film absorbs oxygen and expands when it is oxidized and converted to quartz glass, and the refractive index distribution in (b) is nearly concentric and has a core diameter of 8 μm.
, a relative refractive index difference of O, a O. When connected to a paper-mode optical 7-iper, good results were obtained with a connection loss of 0.3 dB or less. j3-1 The optical waveguide produced by the method of the present invention had a low loss of about 1 dB/cIn.

In the above embodiments, we have explained the process for producing a leading waveguide suitable for connection with a single mode optical fiber, but by increasing the thickness of the a-Ge film and lengthening the diffusion time, It is also possible to form a multi-wire optical waveguide.

As explained above, according to the present invention, it is possible to form a low-loss optical waveguide with excellent compatibility with a silica glass optical fiber through a simple process.

In addition, by changing the shape of the pattern, five types of waveguide optical components such as branching, coupling circuits, and directional couplers can be attached, improving the long-term reliability of optical components as well as optical subscriber systems. It has great utility when applied to fields such as the necessary submarine optical communication.

[Brief explanation of drawings]

Figures 1 (a) to (e) are process diagrams of a conventional glass waveguide manufacturing method and refractive index distribution diagrams of a glass waveguide obtained by the same method, and Figures 2 (f) to 2 (f) are process diagrams of the conventional glass waveguide manufacturing method. A diagram showing an example of the steps of the method and a refractive index distribution diagram of a glass waveguide obtained by the method, FIG. It is a figure showing an example of the refractive index distribution of the glass waveguide obtained by the present invention. 1... Quartz glass substrate, 2... Ge
BIJ, 2 a... Patterned Ge IIL
3... Porous glass film, 2b... Optical waveguide, 4... Transparent glass film, 21...
・S1 film, 22...Ge film, 22a...
・Patterned composite film, 23...Porous glass film, 22b...Optical waveguide, 24...Transparent glass film, 31...Jil origami distribution Central part. Figure 1 Figure 2 Figure 1 (a) Figure 3 (b)

Claims (1)

[Claims] After forming a G film on a glass substrate following the Si film as a diffusion source for controlling the refractive index, both films are patterned into a desired shape by photoetching, and then the glass forming raw material gas is thermally oxidized. Alternatively, a diffusion type is characterized in that fine glass particles synthesized by a hydrolysis reaction are deposited, and then the substrate is heated together to diffuse the diffusion source into the deposited glass and oxidize it, thereby turning the deposited glass into transparent glass. Method for manufacturing glass waveguides.